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Guide Health: The spectre of head lice

No one wants to get the telephone call from your children’s school telling you that several children have been reported to have head lice. But keep in mind that the phone call only means your child plays with many other children, and that you are not alone.

It is estimated that only one to two per cent of the population (including both children and adults) are affected by lice in any one year.

While this number appears small, however, head lice infestations do seem to occur in pockets. Outbreaks occur at one location at a time, for example at a school, and within that school population, the infection rate may be significantly higher.

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Head lice are parasites that feed on human blood. They are scientifically known as Pediculus humanus capitis, and are classified with other types of lice that infest other parts of the body. Lice are about one to three millimetres long with three pairs of legs that end with claws.

You can see them with a magnifying glass, but may not notice an infestation until you see their eggs or nits which are about the size of a grain of rice. An adult female louse lives for about 30 days, during which she can lay seven to 10 eggs per day, for a total of 200 to 300 eggs during her lifetime.

Because head lice are human parasites, they do not survive long away from the human body, usually up to four days.

The first sign of an infestation may be nits along the back and sides of the scalp. The nits attach themselves at the base of the hair shaft, and as the hair grows the nit moves away from the scalp. This means that the farther the nit is away from the scalp, the longer the infestation has been present.

Because the lice may spread their saliva and excrement on your skin as they feed, you may notice itching caused by a sensitivity to this debris.

Pyrethrin 1% (or Nix) is the most often suggested therapy. It is toxic to both adult lice and nits and is considered to be 70 to 100 per cent effective. A second application is usually recommended after seven to 10 days to treat any nits that may have survived and hatched. Pyrethrin can be used by pregnant women and nursing mothers, but for children less than two months, it is not recommended. Unfortunately, some lice may have developed a resistance to this product.

Pyrethrin with piperonyl butoxide (or Rid) is also a pediculicide, but its success rate is only 45 per cent after the first application, and a second application after seven to 10 days is needed to boost the success rate to about 94 per cent. It targets only the adult lice: thus a second application is always needed for the nits that have hatched.

Because both products are related chemically to ragweed and chrysanthemum, people with allergies to these plants need to avoid the two products.

Isopropyl myristate cyclomethicone (or Resultz) is another option. It targets the adult lice by dissolving their exoskeleton. It is not recommended for children under two years, and a second application is needed to eradicate any nits that may have hatched. After the second application, it is considered 82 per cent effective.

Ideally, treatment should resolve the infestation, although treatment failures are common and may be due to a reinfestation. Clothing and linens should be washed in soap and hot water and machine dried using a “hot” setting. Dry cleaning or storing in plastic bags for five to seven days is an option for non-washable items. Rugs, carpets, couches, and mattresses need to be vacuumed.

Nits should be removed from the hair with a fine-tooth comb; soaking the hair with vinegar for 30 to 60 minutes will make the job easier by helping to dissolve the glue that the nit uses to attach itself to the hair shaft. All household contacts of the child need to be treated in order to avoid reinfestation.

You may hear of alternative therapies such as lavender oil, tea tree oil, or even mayonnaise. The idea is that these “smother” the lice. However, no studies show effectiveness. Tea tree oil is also supposed to have antimicrobial and antiseptic properties. However, for lice you need antiparasitic properties. Skin irritation is the most common problem with these products.

If resistance is suspected, try switching to another pediculicide, and remember to treat all household members as well as regular visitors to prevent reinfestation. Nit removal by itself or wet combing, if meticulously done, may be successful. You will need a well-lit area and, depending upon the length and thickness of your child’s hair, several hours. Remember too that nit removal needs to be done every three to four days, continuing for seven days after the last nit is seen.

If the idea of head lice starts you scratching your head, you’re not alone, but keep in mind you can successfully treat them. You just need to be thorough!

About the author


Marie Berry is a lawyer/pharmacist interested in health and education.



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